1) Field of the Invention
The present invention relates to a sealing device and method for sealing a casing. Such casings are for instance used in a wellbore for optionally sealing the casing to e.g. to circulate fluid through the casing.
2) Description of Related Art
U.S. Pat. No. 5,682,952 discloses an extendable casing circulator and method for sealing that may be utilised in either a conventional drilling rig, or in a top drive rig. The sealing device is brought into the casing using an extension device after which a packer element is inflated. This inflated packer element is deflated before withdrawal of the sealing device. In another embodiment the sealing device comprises a top cap that is put over the casing.
Casings that are used in e.g. oil industry show a variation in diameter and/or of their circular shape due to e.g. production tolerances. To bring a sealing device into a casing requires a relatively large gap between the outside diameter of the sealing device and the inside diameter of the casing in order to deal with the variations. Furthermore, there is a variation of nominal diameters between different casings that may increase the opening or gap if these have to be sealed with the same sealing device. This requires additional sealing measures, like an inflatable device, to seal such a gap. Due to the enormous pressure that may occur inside the casing, e.g. in a range of 200-1000 bar due to the e.g. gas pockets, these additional sealing measures may leak, damage etc. Furthermore, the forces acting on an extendable sealing device may become large, thereby requiring large dimensions of such a sealing device.